Hmm.. It's all relative. Calling HR a proxy may be true if you're interested in power output, but it is a measure of your current rate of oxygen consumption. I like to think of it this way: my HR indicates how hard I am working with respect to my own capabilities, my power output over time indicates how hard I am working wrt others and my power to weight ratio over time will give me a proxy to how fast I will go relative to those others. Now due to our rather complex metabolic systems your oxygen requirements vary in non linear ways on your operating environment and how you are generating your power. What cadence you are using can have a strong influence on the HR due to the energy pathways used (phosphogen system vs. glycolysis), and thus the resulting oxygen requirements and corresponding heart rates. I find that using a power meter can be useful in two ways, first in a rather banal way knowing how much power I am putting out, but, more interestingly in a second way where you can use HR and Power combined to gain a better insight in how your body is reacting to exercise in different circumstances and how you can use your gears to adjust your cadence to optimize the power output vs. HR.

Reading the above you may understand why I neither use a power meter nor a HR monitor outside - it distracts me from enjoying my ride, or my focus on the race - I am too much of a geek to ignore quantitative data when I have it at hand. On the trainer looking at these numbers gives me welcome respite from just staring at the wall - I tend to set my training goals for intervals in Watts and judge how I am doing by observing my heart rate in conjunction with my cadence.

Good informative stuff that I would have never thought about. Ben as far as gearing goes I downgraded. I rode nothing but 11-21 until recently (because we were macho and racers) and it became a habit. When I got my new bike it came with 12-26, so I changed it to 11-26 and now I really dig and am still very attached to the 11t. My mtn bike has 13-34 so I am use to spinning with low gearing. I heard that eating the core of pineapple is good for joint pain, anyone has any other remedies.

So it’s not a matter of fitness because I know I am fitter and faster on long rides (but not as explosive) than I was ten years ago, the only thing I have noticed is drop in my HR, and some pain in my knees when going up (plus a few wrinkles). I guess I should be happy that I still can ride.

It sounds to me from the comparisons you are making (legs and knees preventing you from going harder) like it's peak leg force that has declined with age, specifically the amount of fast twitch muscle you have. If you are still trying to push huge gears at slow cadence, but your legs don't have the same % fast twitch muscle they used to, they are going to start to burn and be the limiting factor before they are demanding all the oxygen your heart/lungs is capable of delivering. That means you can't put out as much power (pedal force * cadence) as you used to be able to at lower cadences.

That's not to say you couldn't spin the pedals a little faster at lower force (more slow twitch muscle) and generate similar power levels to what you used to, and probably still get your heart rate up where it used to be. Weight training might be something to consider to help maintain this kind of leg strength.

I'm only 38, and while I'm fitter and can produce more power now than I could at 28, I definitely have less leg stregth and can't do it at as low a cadence as I used to. I also have to have the cadence higher to get to my peak heart rate. I've always had a relatively low peak heart rate, and I used to peak at 186-188bpm at down to 65 cadence. Now I can still get the heart rate up that high, but I need more like minimum 85 cadence to do it. Doesn't matter too much because I can produce more power, even though I need to spin a bit more to do it

It's all relative. Calling HR a proxy may be true if you're interested in power output, but it is a measure of your current rate of oxygen consumption

Exactly the point I was making (with some added emphasis of my own). It is your current rate....but how does that compare against last year, or the year before, etc.? HR does not remain the same through the years, and as already established, diminishes over the years.

Watts are always watts. Further, watts are the "input" while HR is an "output" or byproduct of the input. You are almost always better off measuring the input vs. the byproduct of work to know how much work is being done.

I do agree with your points re: HR changing depending on cadence, even if you keep watts constant. Using HR in combination w/ power, can help identify correct pedaling cadences. Fr me, my HR is lower w/ lower cadence.....but if I do that for too long, my legs get fatigued. So even there, HR can be misleading because it is n it something I can maintain for too long, even though my HR is lower.

CK, I think you got it backwards. Watts is engine output. HR is tied to oxygen and fuel consumption, ie input.

Now you can argue that watts is the input to the transmission, ie the pedals. And that is where it is usually measured. But we don't talk of a car transmission seeing 400 hp. We talk of the engine putting out 400 hp.

I know, picky, picky.

Ben

Edit: another typed smiley face turns yellow. Maybe I will get used to this.

Just for clarity - I am not arguing with you - just furthering the discussion.

I am confused as how you consider power [Watts] an input? Wattage is normally used as either an output (think engine power) or a consumption characterization (think light bulb) parameter. In the case of a power meter on a bike we are by definition measuring an output parameter resulting from a highly complex process.

Watts may always be Watts, but that is analogue to beats per minute are always beats per minute i.e. a standard unit for measurement.

Anyway - it seems that we mostly agree, other than that I think power and HR are complementary measures of what our bodies are doing, rather than proxies of each other (although from your last paragraph - we agree on that too?)

I guess when I was referring to power as an input, I was referring to it relative to the bike, not the body. It is the input that drives the bike forward. Does that make sense? In terms of the body's performance, you are correct...it is an output.

The difference between watts and BPM is that watts are objective. If it takes XX watts to go 20 mph for a given set of conditions, it will always take XX watts to go 20 mph for that same set of conditions. Your fitness level has no bearing on watts (other than being able to hold them!). HR can vary depending on any number of circumstances....temperature, cadence, fitness, hydration, etc.

HR has the "most" value, IMO, in the early season. As your season progresses, it becomes increasingly non-important. I don't even look at my HR anymore on the bike. There may be times when I check it if I feel I am struggling..."jeez, why does 200w feel so freakin' hard today?"...but that is just a fancy PE check.

There are some applications where it can tell you some valuable info (see our discussion re: cadence) but even there it can be misleading (and should ideally be used in conjunction with power). A lower HR is not necessarily a good thing if it leads to premature muscle fatigue....as can happen to me if I keep a low cadence (<80) for too long. Yeah, my HR is lower, but it is taking a bigger psyiological toll on my body that is not reflected in the HR.

But again if power is not an option, HR is the best alternative. It was, for decades, the gold standard as a training tool. But power has clearly supplanted it.

My (bike) max HR hasn't dropped much in 20 years but what has been dropping is my average HR for hard efforts/races. It was pretty common for me to have an average HR or 175-180 for most races. Now, even on the same courses, I'm in the upper 160 to lower 170s.

I am now even more confused re. input and output - if the statement was relative to the bike, then HR is logically an output of the bike? Anyway, I think this has become an issue of semantics; which it is not worth spending our energy on.

It strikes me that you are discussing HR vs. power data in the sense of which is 'better' than the other. I guess it is worth considering which contains more useful information if we had to choose. That is not a realistic choice considering that power meters are an order of magnitude more expensive than HR monitors, and thus if we can afford a power meter we can easily afford the incremental cost of a HR strap (for most systems that is the only extra bit of hardware needed) . However, if I had to make the decision I would, like you, choose the power meter. Because the environmental effects will be correlated stronger to both RPE and HR than power, and RPE and HR are correlated well enough (but not linearly related!) that with common sense and experience how they interact RPE is a useful alternative.

However, for all the reasons that you listed in your last post as an argument against using HR I want to have the HR monitor. It gives me an indication of how a number of circumstances e.g. .temperature, cadence, fitness, hydration, etc. (to borrow your list ) are affecting my body i.e., system performance and so helps explain why the very simple parameter (power) that determines how fast we are going at an instant comes about. To really be effective in characterization you need to take into account that whole list of parameters that you named (and the etc. contains a lot of them :0 ), some of which are easy to characterize (temperature, humidity), some of which are hard to characterize (mental state, blood lactate level, hydration state, oxygen consumption) and some of which are very hard to characterize (nutritional state). Off course, I left out many other factors that could affect performance. It would be ideal, but certainly not practical, to be able to monitor all these factors affecting out performance, resulting in that simple single output number: power. Even though HR and power are only two of many possible parameters they together with our senses allow us to characterize our efforts pretty completely.

I agree that HR can be easily misinterpreted if used as simply as saying that a lower HR rate is better - as you point out, that is not necessarily the case. It depends on what your immediate goals are to figure out what a good target HR for you at that moment is. However, that is just as true for power - simply saying more power is better is not going to get you far if you do not think about what your goals are. This is after all why there are entire books written about training with power.

Actually most horsepower in cars is measured at the wheels "brake" horsepower. Some take the engine off and put it on an engine dyno. Horsepower on bikes can be measured at pedals, cranks, hubs... depends on the system. They are about equivalent assuming little power lose to the drivetrain. Watts is power, the rate of doing work. Heart rate is about oxygen delivery and is only part of the equation along with stroke volume, hematocrit, etc. Cardiac output = stroke volume x HR. Oxygen delivery = cardiac output x hematocrit + disolved oxygen (not usually important) With aerobic training max heart rate typically goes down not up. As we get older our max heart rate gets slower. Critical power is the power output you can sustain for a certain duration. It is what matters most. For 99% of cyclist who cares, RIDE YOUR BIKE.

Same power output at a lower HR probably means better efficiency. The energy cost of doing work. But really... get a life. After a master's degree in applied exercise physiology and an MD... I could care less. How fast am I from point a to point b. Did I kick the other guy's ass or did he kick mine. All I need to know. The biggest advantage of heart rate is in gauging effort. A lot of recreational cyclists probably over do it from time to time. HR can let you know when you need to ease off a bit... higher morning resting HR, higher HR for same effort = need some active rest. Power is great but really power to weight ratio = speed. If you ride the same courses and with the same people you know if your power is up or down even if you don't know the exact number.

I totally agree GC - that's why I don't ride with a power meter outside - I do think it is more entertaining to think about this stuff on the trainer than staring at the wall ( I tried watching movies, but that doesn't do it for me)

Posted By Carbon Gecko on 05/16/2013 08:44 PM
Power is great but really power to weight ratio = speed.

No, this is not accurate. Power to weight = speed going uphill. But on the flats (or even on rolling hills) power to weight doesn't tell you much. On the flats, it is about power-to-CDa, which is a more direct translation to speed.